All-in.

Since he posted and called we can discount pairs since he will call a lot of unpaired hands he otherwise would have folded pre-flop. If we're beat he's just on 2 pair and we have a fair chunk of equity against him. He certainly could be playing top pair like this (to defend against a draw) or a draw (to get us to fold or at least get the money in pretty good.)

Putting him on a tighter range than that seems silly to me.